首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   399964篇
  免费   45776篇
  国内免费   363篇
  2016年   3668篇
  2015年   5485篇
  2014年   6395篇
  2013年   9243篇
  2012年   10349篇
  2011年   10384篇
  2010年   6921篇
  2009年   6499篇
  2008年   9287篇
  2007年   9764篇
  2006年   9315篇
  2005年   9050篇
  2004年   8932篇
  2003年   8498篇
  2002年   8521篇
  2001年   18310篇
  2000年   18857篇
  1999年   14990篇
  1998年   4994篇
  1997年   5210篇
  1996年   4867篇
  1995年   4671篇
  1994年   4619篇
  1993年   4601篇
  1992年   12113篇
  1991年   11683篇
  1990年   11358篇
  1989年   10986篇
  1988年   10376篇
  1987年   9899篇
  1986年   9403篇
  1985年   9502篇
  1984年   7862篇
  1983年   6763篇
  1982年   5389篇
  1981年   5018篇
  1980年   4568篇
  1979年   7653篇
  1978年   6176篇
  1977年   5670篇
  1976年   5363篇
  1975年   6020篇
  1974年   6645篇
  1973年   6595篇
  1972年   6090篇
  1971年   5515篇
  1970年   4758篇
  1969年   4723篇
  1968年   4306篇
  1967年   3623篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
With the use of anticoagulants to prevent recurrence of thrombosis it is now possible to open a major artery which has been occluded by a thrombus, remove the thickened lining with the clot and restore the continuity of the vessel. Free vein grafts have been used successfully to replace arterial segments in the extremities. Vein inlay grafts are preferred in dealing with aneurysms of the abdominal aorta. The aneurysmal wall can be used to support the venous segments. It has been possible to by-pass aneurysms of the abdominal aorta by anastomosing the splenic artery to the left iliac artery. The use of the left superficial femoral artery as a by-pass to supply blood to the right leg is described.  相似文献   
995.
Abstract An investigation has been made of the resistance time and upper lethal temperature of ammocoetes of four species of lampreys provided with a substrate into which they could readily burrow. In general, ammocoetes burrowed after transfer from the acclimation to the experimental temperature baths and later came out of the substrate only in lethal temperatures. A relationship was observed between the resistance time and the time taken to emerge, with the resistance time increasing exponentially with decreasing experimental temperature. In Ichthyomyzon fossor, landlocked Petromyzon marinus, Lampetra (Lethenteron) Lamottenii and in Lampetra (Lampetra) planeri from two different times of the year, the incipient lethal levels over a two week experimental period for larvae acclimated to 15° G were respectively 30.5, 30, 29.5, 28.5 and 28° C. Values for P. marinus acclimated to 5 and 25° C were respectively 29.5 and 31° C, whereas in L. planeri they were 28 and 29° C in April/May and 27 and 29° C in July/August. Extrapolation of the results for the three acclimation temperatures yielded ultimate incipient lethal levels of 31.4° G in P. marinus and 29.2 and 29.4° C for L. planeri examined in the spring and summer respectively.  相似文献   
996.
The anatomical basis for the application of neurovascular pedicled muscle transfers of the digastric and stylohyoid muscles in the treatment of velopharynx incompetence is described. The fact that the neurovascular pedicle is located in the cranial third of the muscle bellies provides the safety of the operative procedure. The muscles have to be dissected with respect to that. The direction in which the transferred muscles pull is described. The muscle transposition is combined with the classic Wardill-Kilner operation to lengthen the soft palate. The transferred muscles have to avoid scar contraction and shortening of the soft palate and to gain a muscular function of the soft palate. The clinical use is justified in rare cases as demonstrated in one case.  相似文献   
997.
    
Ohne Zusammenfassung  相似文献   
998.
999.
WARTS     
  相似文献   
1000.
The sensitivity of the fluorescent dye, 3,3′-diethylthiadicarbocyanine (DiS-C2(5)), was too low for the detection of membrane potential changes in rat small intestinal membrane vesicles. Only after adding LaCl3 or after fractionation of the intestinal membranes by free-flow electrophoresis could the dye be used to monitor electrogenic Na+-dependent transport systems. It is concluded that the response of this potential-sensitive dye is influenced by the negative surface charge density of the vesicles.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号